Jun 30, 2015
Scouting insects in high tunnels

We just returned from the University of Vermont where we, along with researchers from the University of Maine, participated in an intensive training program on scouting and identifying insects in high tunnels. Our training was hosted by Dr. Margaret Skinner and Cheryl Sullivan, Entomologists at the University of Vermont.

Scouting for insect pests in high tunnels is commonly done in two ways:

  • Monitoring sticky cards

  • Random plant inspection

Sticky cards can be found in a few colors with yellow being used to attract the widest audience of insects. Sticky cards are used to monitor winged insects. Common flying insects found in high tunnels include the following pests: fungus gnats, thrips, whiteflies, leafhoppers, and winged aphids. Natural enemies include parasitic wasps, hover flies, lacewings, lady bird beetles, and Aphidoletes sp. When developing a scouting plan for a crop, it's important to know what insect pests to expect. Start by looking up what pests are commonly found on the crop or crops produced in the high tunnels. For example, flea beetles are commonly found on eggplant and cucumber beetles on cucumbers. On our farm visits, we know to watch out for these pests and find these insects on sticky cards and during our random plant inspection of these crops. There will be a number of other insects on the sticky cards that are largely of limited value for making pest management decisions. This is another reason why it is important to know what pests you should be looking for.

Yellow sticky cards can be used in different ways. The instructions we received recommend they be hung from the roof of the structure or attached to a stake above the plant canopy.

For our project we are attaching them 4-6 inches above the ground to plastic or natural bamboo stakes with binder clips or clothes pins and placing one card every 1,000 square feet.

We are changing our cards every 2 weeks, however, they can be changed on a more frequent basis while implementing pest management strategies. Sticky cards with insects can be placed in a plastic baggie for easy and “goo free” observation. A marker then can be used to circle and count important insects.

Random plant inspection is used to monitor winged and wingless insects. This is the only way to monitor pests like wingless aphids and spider mites, which will not be found on the sticky cards. There are many ways to scout. Penn State Extension's Vegetable Integrated Pest Management with an Emphasis on Biocontrol has procedures for scouting various crops as well as action thresholds and is available for purchase.

We scout by inspecting 5 plants every 100 linear feet of row. Once we select a plant, we take a moment to observe the plant to see what's there – insects and any abnormal plant growth.

Then, we scout the plant in 3 sections: upper, middle and lower. We examine the upper and lower surface of 3 leaves in each section.

Lastly, we will gently tap the plant over a white sheet of paper – this is a great way to detect thrips in particular. If we see a pest in any of these steps we record what we see and flag the plant so that we can keep monitoring the area.

Hand lenses are inexpensive tools that greatly help with seeing small insects. They are available with varying powers of magnification: 10x, 16x and 20x, for example. We are using a 20x lens for our project. When using a hand lens, hold it close to your eye – about a fingers width away. Then either move your head close to the object or bring the object close to your eye.

We were also introduced to “hands-free” optivisors and handheld lenses with a cup for trapping insects for observation. It's truly a matter of personal preference, but all of the above tools are very valuable for magnifying small insects.

Developing a scouting plan that includes sticky cards and random plant inspection can help you catch pest hotspots before they spread throughout the crop and are an important step in integrated pest management.

— By Elsa Sánchez, Associate Professor of Horticultural Systems Management, Penn State University


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